U.S. patent application number 11/116579 was filed with the patent office on 2006-11-02 for hard coats with a cationic acrylic polymer.
Invention is credited to Shan Cheng, David R. Fenn, Brian K. Rearick, Steven R. Zawacky.
Application Number | 20060247348 11/116579 |
Document ID | / |
Family ID | 36950188 |
Filed Date | 2006-11-02 |
United States Patent
Application |
20060247348 |
Kind Code |
A1 |
Cheng; Shan ; et
al. |
November 2, 2006 |
Hard coats with a cationic acrylic polymer
Abstract
A hard coat composition comprising a cationic acrylic polymer is
disclosed. The hard coat is suitable for application to a
substrate, and can be used without an adhesive promoting
primer.
Inventors: |
Cheng; Shan; (Pittsburgh,
PA) ; Fenn; David R.; (Allison Park, PA) ;
Rearick; Brian K.; (Allison Park, PA) ; Zawacky;
Steven R.; (Pittsburgh, PA) |
Correspondence
Address: |
PPG Industries, Inc.;Law Dept. - Intellectual Property
One PPG Place
Pittsburgh
PA
15272
US
|
Family ID: |
36950188 |
Appl. No.: |
11/116579 |
Filed: |
April 28, 2005 |
Current U.S.
Class: |
524/265 ;
524/556 |
Current CPC
Class: |
C09D 133/14 20130101;
C08L 83/00 20130101; C09D 183/04 20130101; C09D 133/068 20130101;
C08L 83/00 20130101; C09D 133/068 20130101; C08L 83/04 20130101;
C09D 133/14 20130101 |
Class at
Publication: |
524/265 ;
524/556 |
International
Class: |
B60C 1/00 20060101
B60C001/00; C08K 5/24 20060101 C08K005/24 |
Claims
1. A hard coat composition comprising a cationic acrylic
polymer.
2. The composition of claim 1, wherein the cationic acrylic polymer
contains a sulfonium moiety.
3. The composition of claim 1, wherein the cationic acrylic polymer
comprises glycidal (meth)acrylate.
4. The composition of claim 1, wherein the cationic acrylic polymer
contains 0.01 to 3 milliequivalents of cationic salt groups per
gram of polymer solids.
5. The composition of claim 1, further comprising an alkoxide.
6. The composition of claim 5, wherein the alkoxide is
organoalkoxysilane.
7. The composition of claim 6, wherein the organoalkoxysilane is
partially or fully hydrolyzed.
8. A method for improving adhesion between a hard coat and a
substrate, comprising adding to the hard coat a cationic acrylic
polymer.
9. The method of claim 8, wherein the substrate is
thermoplastic.
10. The composition of claim 9, wherein the substrate comprises
polycarbonate.
11. The method of claim 8, wherein the composition further
comprises an alkoxide.
12. The method of claim 11, wherein the alkoxide is
organoalkoxysilane.
13. The method of claim 12, wherein the organoalkoxysilane is
partially or fully hydrolyzed.
14. A method for improving a property of a substrate, comprising
applying to at least a portion of the substrate the coating of
claim 1.
15. The method of claim 14, wherein the substrate is
thermoplastic.
16. The method of claim 15, wherein the substrate is
polycarbonate.
17. The method of claim 14, wherein the coating further comprises
an alkoxide.
18. The method of claim 17, wherein the alkoxide is
organoalkoxysilane.
19. The method of claim 18, wherein the organoalkoxysilane is
partially or fully hydrolyzed.
20. The method of claim 18, wherein the coating has a dry film
thickness of 5 to 7 microns.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to hard coat compositions
comprising a cationic acrylic polymer.
BACKGROUND INFORMATION
[0002] Plastic substrates, including transparent plastic
substrates, are desired for a number of applications, such as
windshields, lenses and consumer electronics. To minimize
scratching, as well as other forms of degradation, clear "hard
coats" are often applied as protective layers to the substrates. A
primer is often used to enhance adhesion between the hard coat and
the substrate. Hard coats that adhere to these substrates without
the use of a primer are desired.
SUMMARY OF THE INVENTION
[0003] The present invention is directed to hard coat compositions
comprising a cationic acrylic polymer. The present invention is
further directed to a method for improving adhesion of a hard coat
to a substrate comprising adding to the hard coat a composition
comprising a cationic acrylic polymer. The present invention is
also directed to a method for improving a property of a substrate
comprising applying to the substrate a coating comprising a
cationic acrylic polymer.
DETAILED DESCRIPTION OF THE INVENTION
[0004] The present invention is directed to hard coat compositions
comprising a cationic acrylic polymer resin. The term "hard coat,"
as used herein, refers to a clear coat that offers one or more of
chip resistance, impact resistance, abrasion resistance, UV
degradation resistance, humidity resistance and/or chemical
resistance. Any composition that comprises a cationic acrylic
polymer can be used according to the present invention. A "cationic
acrylic polymer" refers to acrylic polymers that comprise cationic
functional groups that impart a positive charge.
[0005] The cationic acrylic polymer can be formed by any means
known in that art. Suitable cationic acrylic polymers include, for
example, copolymers of one or more alkyl esters of acrylic acid or
methacrylic acid, optionally together with one or more other
polymerizable ethylenically unsaturated monomers. Suitable alkyl
esters of acrylic acid or methacrylic acid include, without
limitation, methyl methacrylate, ethyl methacrylate, butyl
methacrylate, ethyl acrylate, butyl acrylate, and 2-ethyl hexyl
acrylate. Suitable other copolymerizable ethylenically unsaturated
monomers include nitrites, such as acrylonitrile and
methacrylonitrile, vinyl and vinylidene halides, such as vinyl
chloride and vinylidene fluoride, and vinyl esters, such as vinyl
acetate, among other monomers. Acid and anhydride functional
ethylenically unsaturated monomers, such as acrylic acid,
methacrylic acid or anhydride, itaconic acid, maleic acid or
anhydride, or fumaric acid may be used. Amide functional monomers
including, without limitation, acrylamide, methacrylamide, and
N-alkyl substituted (meth)acrylamides are also suitable. Vinyl
aromatic compounds, such as styrene and vinyl toluene, can also be
used in certain cases.
[0006] Functional groups, such as hydroxyl and amino groups, can be
incorporated into the acrylic polymer by using functional monomers,
such as hydroxyalkyl acrylates and methacrylates or aminoalkyl
acrylates and methacrylates. Epoxide functional groups (for
conversion to cationic salt groups) may be incorporated into the
acrylic polymer by using functional monomers, such as glycidyl
acrylate and methacrylate, 3,4-epoxycyclohexylmethyl(meth)acrylate,
2-(3,4-epoxycyclohexyl)ethyl(meth)acrylate, or allyl glycidyl
ether. Alternatively, epoxide functional groups may be incorporated
into the acrylic polymer by reacting carboxyl groups on the acrylic
polymer with an epihalohydrin or dihalohydrin, such as
epichlorohydrin or dichlorohydrin.
[0007] Suitable acrylic polymers can be prepared by traditional
free radical initiated polymerization techniques, such as solution
polymerization techniques, as known in the art using suitable
catalysts, which include organic peroxides and azo type compounds,
and optionally chain transfer agents, such as alpha-methyl styrene
dimer and tertiary dodecyl mercaptan.
[0008] In certain embodiments, the cationic acrylic polymer can be
an amino group containing resin that is rendered cationic by at
least partial neutralization of the amino groups with an acid.
Suitable acids include organic and inorganic acids such as formic
acid, acetic acid, lactic acid, phosphoric acid,
dimethylolpropionic acid and sulfamic acid. Mixtures of acids can
be used. In certain embodiments, the resin can contain primary,
secondary and/or tertiary amino groups. Amino groups can be
introduced into the copolymer directly by using an amino group
containing monomer such as an aminoalkyl (meth)acrylate, for
example dimethylaminopropyl methacrylate. Alternatively the amino
groups can be derived from the reaction of an epoxide functional
acrylic polymer with a compound containing a primary or secondary
amine group, such as methylamine, diethanolamine, ammonia,
diisopropanolamine, N-methyl ethanolamine, diethylentriamine,
dipropylenetriamine bishexamethylenetriamine, the diketimine of
diethylentriamine, the diketimine of dipropylenetriamine, the
diketimine of bishexamethylenetriamine and mixtures thereof.
Non-limiting examples of suitable cationic acrylic polymers
containing amino groups include those resins described in U.S. Pat.
Nos. 3,455,806 and 3,928,157 and published application 2003/0054193
A1, all of which are hereby incorporated by reference.
[0009] In certain embodiments, the cationic acrylic polymer can be
a sulfonium salt group containing resin. Sulfonium salt groups can
be introduced by the reaction of an epoxy group with a sulfide in
the presence of an acid. Suitable cationic acrylic polymers
containing sulfonium salt groups include those resins described in
U.S. Pat. Nos. 3,959,106, and 4,038,232, and published application
2003/0098238, all of which are hereby incorporated by
reference.
[0010] In certain embodiments, the cationic acrylic polymer
contains 0.01 to 3, such as 0.1 to 1, milliequivalents of cationic
salt groups per gram of polymer solids.
[0011] The hard coat compositions of certain embodiments of the
present invention can further comprise an alkoxide having the
general formula R.sub.xM(OR').sub.z-x where R is an organic
radical, M is silicon, aluminum, titanium, and/or zirconium, each
R' is independently an alkyl radical, z is the valence of M, and x
is a number less than z and may be zero. Examples of suitable
organic radicals include, but are not limited to, alkyl, vinyl,
methoxyalkyl, phenyl, .gamma.-glycidoxy propyl and/or
.gamma.-methacryloxy propyl. The alkoxide can be unhydrolyzed,
partially hydrolyzed or fully hydrolyzed. The alkoxide can be
further mixed and/or reacted with other compounds and/or polymers
known in the art, such as compositions comprising siloxanes formed
from at least partially hydrolyzing an organoalkoxysilane, such as
one within the formula above. Examples of suitable
alkoxide-containing compounds and methods for making them are
described in U.S. Pat. Nos. 6,355,189; 6,264,859; 6,469,119;
6,180,248; 5,916,686; 5,401,579; 4,799,963; 5,344,712; 4,731,264;
4,753,827; 4,754,012; 4,814,017; 5,115,023; 5,035,745; 5,231,156;
5,199,979; and 6,106,605, all of which are incorporated by
reference herein. A suitable commercially available alkoxide hard
coat from PPG Industries, Inc. is SOLGARD 330.
[0012] The hard coat compositions of the present invention can also
include one or more standard additives, such as UV absorbers, flow
additives, rheology modifiers, adhesion promoters, catalysts,
pigments, dyes and the like. In certain embodiments, the UV
absorber is silylated. Silylated UV absorbers are commercially
available from Gelest, Inc. It may also be desired to add
crosslinkers, to react with any functionality introduced by the
acrylic or the compound used to form the salt.
[0013] Typically, the cationic acrylic polymer will be present in
the hard coat composition in an amount of 1 to 25 weight percent,
such as 2 to 15 or 5 to 10 weight percent, with weight percent
being based on the total solid weight of the composition. When an
alkoxide is also used in the composition, it will typically
comprise 50 to 99 weight percent, based on total solidweight.
[0014] If a cationic acrylic polymer is used with a partially or
fully hydrolyzedalkoxide, it can simply be added to the alkoxide
with stirring. In certain embodiments, rather than post-adding a
cationic acrylic polymer to an unhydrolyzed or partially hydrolyzed
alkoxide coating, the alkoxy silane precursors and cationic acrylic
polymer can be co-hydrolyzed. This can be done using methods
standard in the art. A silylated UV absorber can also be used in
the reaction.
[0015] Acrylics may not be compatible with partially or fully
hydrolyzed alkoxide. Forming the cationic salt of the acrylic helps
to compatibilize the acrylic and alkoxide.
[0016] In certain embodiments of the present invention, the hard
coat composition does not comprise a polycaprolactone polyol,
and/or a (meth)acrylate that is not in cationic salt form.
[0017] The present invention is also directed to a method for
improving adhesion between a hard coat and a substrate comprising
adding to the hard coat a cationic acrylic polymer. The cationic
acrylic polymer is as described above. Any amount of improved
adhesion is within the scope of the present invention; whether
improved adhesion is observed can be easily determined using
testing standard in the art, such as cross hatch tape adhesion
testing, abrasion resistance testing and the like. Comparing the
results obtained with a hard coat both with and without the
cationic acrylic polymer described above will indicate whether
improved adhesion is achieved.
[0018] The present invention is further directed to a method for
improving a property of a substrate comprising applying to the
substrate a coating comprising a cationic acrylic polymer, such as
any of the coatings described above. As used herein, "improving a
property" and like terms refers to improving a property of the
substrate such as chip resistance, impact resistance, abrasion
resistance, UV degradation resistance, humidity resistance and/or
chemical resistance including but not limited to alkali
resistance.
[0019] Suitable substrates that can be treated according to the
present invention generally include plastic substrates, such as
thermoplastic substrates, including but not limited to
polycarbonates, acrylonitrile butadiene styrene, blends of
polyphenylene ether and polystyrene, polyetherimides, polyesters,
polysulfones, acrylics, and copolymers and/or blends of any of
these. The coating comprises the cationic acrylic polymer, as
described above. The coating can also further comprise an alkoxide
and/or any standard additives, also as described above.
[0020] The coating composition can be applied to the substrate by
any means known in the art, such as spraying, dipping, roll
coating, flow coating, brushing, and the like. The coating can then
be cured, such as by flashing the coating at ambient temperature
for up to one hour, and then baking the coating at an appropriate
temperature and time, which can be determined by one skilled in the
art based upon the particular coating and/or substrate being used.
It will be appreciated that any suitable cure conditions can be
used, and will depend on the particular formulation of the coating
applied. The dry film thickness of the coating on the substrate can
be from 1 to 10 microns, such as 5 to 7 microns. The coating can be
applied directly to the substrate without a primer or other
intervening layer with suitable adhesion being observed.
[0021] As used herein, unless otherwise expressly specified, all
numbers such as those expressing values, ranges, amounts or
percentages may be read as if prefaced by the word "about", even if
the term does not expressly appear. Any numerical range recited
herein is intended to include all sub-ranges subsumed therein.
Plural encompasses singular and vice versa. For example, while the
coatings of the present invention have been described in terms of
"a" cationic acrylic polymer, one or more such acrylics can be
used. Also, as used herein, the term "polymer" is meant to refer to
prepolymers, oligomers and both homopolymers and copolymers; the
prefix "poly" refers to two or more.
EXAMPLES
[0022] The following examples are intended to illustrate the
invention, and should not be construed as limiting the invention in
any way.
Example 1
[0023] The coating solutions were prepared as follows: A cationic
acrylic polymer adhesion promoter solution was added into
alkoxysilane hard coat solutions (SOLGARD 330, from PPG Industries,
Inc.) under stirring as indicated in Table 1 below.
[0024] MOKROLON polycarbonate substrate from Bayer was wiped and
rinsed with 2-propanol. Coatings were flow or spray applied on
un-primed substrate and flashed at ambient for 5 minutes. The
coated polycarbonate was baked at 120.degree. C. for 3 hours. The
dry film thickness of the coating was 5-10 .mu.m. Coated panels
were tested for adhesion and taber abrasion resistance.
[0025] As demonstrated in Table 1, coatings without the cationic
acrylic polymer adhesion promoter did not provide acceptable
adhesion. Without acceptable adhesion, coatings do not exhibit
abrasion resistance. Therefore only the samples that passed the
adhesion test were evaluated for taber abrasion resistance.
TABLE-US-00001 TABLE 1 Compositional Information on Primerless Hard
Coat Formulations and Performance Example 1 2 3 4 5 Component A*
Pre-hydrolyzed 25 25 25 20 15 Alkoxysilane Coating.sup.1
Solvent.sup.2 25 25 25 20 15 Component B* Amine Salt Cationic --
0.20 1.0 -- -- acrylic polymer Resin Solution.sup.3 Amine Salt
Cationic -- -- -- 0.12 -- acrylic polymer Resin Solution.sup.4
Sulfonium Salt Cationic -- -- -- -- 0.09 acrylic polymer Resin
Solution.sup.5 Melamine Resin -- 0.03 0.13 -- -- Solution.sup.6
Acid Catlyst.sup.7 -- 0.01 0.06 -- -- Solvent.sup.8 -- 0.26 1.32
0.68 0.51 Testing Results Appearance.sup.9 Clear Clear Clear Clear
Slightly milky Initial Haze %.sup.10 -- 0.2 0.3 1.2 3.6
Adhesion.sup.11 -- 5 5 5 5 Delta Haze % after -- 12 18 16 -- Taber
Abrasion.sup.12 *Based on weight of each component. .sup.1SOLGARD
.TM. 330, PPG Industries, Inc. .sup.21-propanol. .sup.3Amine salt
cationic acrylic polymer resin, MW = 12300, 57% total solid,
prepared according to Example 2. .sup.4Amine salt cationic resin,
Mw-22400, 56% total solid, prepared according to Example 3.
.sup.5Sulfonium salt acrylic resin, Mw = 22400, 57% total solid,
prepared according to Example 4. .sup.6CYMEL 327, Cytec Industries
Inc. .sup.7Phenyl acid phosphate solution, KOCK Chemical. Diluted
to 10% in 1-propanol. .sup.81-propanol. .sup.9As visually observed
after cure. .sup.10Measured with Ultra Scan XE spectrophotometer
from Hunter Associates Laboratory. .sup.11Adhesion: Crosshatch,
Nichibon LP-24 adhesive tape. Rating scale 0-5 (0 = no adhesion; 5
= 100% adhesion after tape peeling). .sup.12Taber Abrasion: Taber
5150 Abrader, CS-10 wheels, 500 grams weight. Haze % was measured
after 500 taber abrasion cycles.
Example 2
[0026] TABLE-US-00002 Charge Weight A Butyl Cellosolve.sup.13 135.3
Deionized Water 14.0 B Butyl acrylate 49.0 Methyl methacrylate 56.0
Styrene 350.0 Glycidyl methacrylate 105.0 Hydroxypropyl 140.0
methacrylate t-Dodecyl mercaptan 23.0 VAZO 67.sup.14 17.6 Butyl
Cellosolve 14.0 C LUPEROX 26.sup.15 7.3 Butyl Cellosolve 29.5 D
Diethanolamine 73.5 Butyl Cellosolve 6.7 E Butyl Cellosolve 3.3 F
Deionized Water 37.5 G n-Propanol 274.5 H 88% Lactic Acid.sup.16
57.3 I n-Propanol 100.0 .sup.13ethyleneglycol monobutyl ether
available from Dow Chemical Co.
.sup.142,2'-azobis(2-methylbutyronitrile) available from E.I.
DuPont de Nemours & Co. .sup.15t-Butyl peroxy-2-ethylhexanoate
available from Arkema. .sup.1688% aqueous lactic acid available
from Purac America Inc.
Resin Preparation Method
[0027] Charge A was added to a flask fitted with a nitrogen inlet,
stirrer, condenser and thermocouple. The mixture was heated to 100
to 105.degree. C. and charge B was then added dropwise at a uniform
rate over 21/2 hours while maintaining the reaction temperature
between 100 to 105.degree. C. After charge B was in, the mixture
was held at temperature a further 30 minutes, and then charge C was
added at a uniform rate over 15 minutes while maintaining the
reaction temperature at 100 to 105.degree. C. After an additional
30 minutes hold at temperature, the temperature raised to 110 to
115.degree. C. When the temperature had stabilized, charge D was
added at once and the mixture allowed to exotherm and then was held
at 120 to 125.degree. C. for 2 hours. When the hold was over,
Charges E and F were added while the reaction mixture was cooled to
90 to 95.degree. C. When the temperature was reached, Charges G, H
and I were added dropwise in turn to give the final product. The
material was filled out warm and cooled to give a resin with 57.14%
solids and a measured meq acid of 0.329 and meq base of 0.496 per
gram.
Example 3
[0028] TABLE-US-00003 Charge Weight A Butyl Cellosolve.sup.17 135.3
Deionized Water 14.0 B Butyl acrylate 49.0 Methyl methacrylate 56.0
Styrene 350.0 Glycidyl methacrylate 35.0 Hydroxypropyl 210.0
methacrylate t-Dodecyl mercaptan 7.0 VAZO 67.sup.18 17.5 Butyl
Cellosolve 14.0 C LUPEROX 26.sup.19 7.3 Butyl Cellosolve 29.5 D
Butyl Cellosolve 13.6 E Diethanolamine 24.5 Butyl Cellosolve 6.7 F
Deionized Water 37.5 G n-Propanol 274.5 H 88% Lactic Acid.sup.20
19.1 I n-Propanol 105.1 .sup.17ethyleneglycol monobutyl ether
available from Dow Chemical Co.
.sup.182,2'-azobis(2-methylbutyronitrile) available from E.I.
DuPont de Nemours & Co. .sup.19t-Butyl peroxy-2-ethylhexanoate
available from Arkema. .sup.2088% aqueous lactic acid available
from Purac America Inc.
Resin Preparation Method
[0029] Charge A was added to a flask fitted with a nitrogen inlet,
stirrer, condenser and thermocouple. The mixture was heated to 100
to 105.degree. C. and charge B was then added dropwise at a uniform
rate over 21/2 hours while maintaining the reaction temperature
between 100 to 105.degree. C. After charge B was in, the mixture
was held at temperature a further 30 minutes, and then charge C was
added at a uniform rate over 15 minutes while maintaining the
reaction temperature at 100 to 105.degree. C. After an additional
30 minutes hold at temperature, the temperature raised to 110 to
115.degree. C. while adding charge D. When the temperature had
stabilized, charge E was added at once and the mixture allowed to
exotherm and then was held at 120 to 125.degree. C. for 2 hours.
When the hold was over, Charge F was added while the reaction
mixture was cooled to 90 to 95.degree. C. When the temperature was
reached, Charges G, H and I were added dropwise in turn to give the
final product. The material was filled out warm and cooled to give
a resin with 55.5% solids and a measured meq acid of 0.117 and meq
base of 0.173 per gram.
Example 4
[0030] TABLE-US-00004 03-017-112 A Butyl Cellosolve.sup.21 135.3
deionized water 14.0 B Butyl acrylate 49.0 Hydroxypropyl 210.0
methacrylate Methyl methacrylate 56.0 styrene 350.0 Glycidyl
methacrylate 35.0 t-dodecyl mercaptan 7.0 VAZO 67.sup.22 17.5 Butyl
Cellosolve 14.0 C LUPEROX 26.sup.23 7.3 Butyl Cellosolve 29.5 D
Butyl Cellosolve 20.3 E thiodiethanol 56.9 acetic acid 14.0
deionized water 21.0 F n-propanol 396.7 .sup.21ethyleneglycol
monobutyl ether available from Dow Chemical Co.
.sup.222,2'-azobis(2-methylbutyronitrile) available from E.I.
DuPont de Nemours & Co. .sup.23t-butyl peroctoate available
from Arkema
Resin Synthesis Procedure (i) Polymerization Stage
[0031] Components A were charged to a flask fitted with a nitrogen
inlet, stirrer, condenser and thermocouple. The temperature was
increased to 100.degree. C. and this temperature was maintained
throughout the polymerization stage. Components B were then added
at a uniform rate over 150 minutes. 30 minutes later, components C
were added over about 10 minutes. After a further 30 minutes, the
heat source was removed and the reaction mixture was allowed to
cool.
(ii) Sulfonium Stage
[0032] Once the temperature had reached 80.degree. C. the heat
source was replaced and components D and E were added. The
temperature was adjusted back to 80 C and maintained for 5 hours.
Titration of a sample at this stage revealed that the sulfonium
content was 0.053 milliequivalents/g, the epoxy equivalent weight
was 8655 and the acid value was 8.0. Component F was added and the
resin solution was allowed to cool to room temperature.
[0033] Whereas particular embodiments of this invention have been
described above for purposes of illustration, it will be evident to
those skilled in the art that numerous variations of the details of
the present invention may be made without departing from the
invention as defined in the appended claims.
* * * * *